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drivers/base: Fix length checks in create_syslog_header()/dev_vprintk_emit()

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snprintf() returns the number of bytes that could have been written
(excluding the null), not the actual number of bytes written.  Given a
long enough subsystem or device name, these functions will advance
beyond the end of the on-stack buffer in dev_vprintk_exit(), resulting
in an information leak or stack corruption.  I don't know whether such
a long name is currently possible.

In case snprintf() returns a value >= the buffer size, do not add
structured logging information.  Also WARN if this happens, so we can
fix the driver or increase the buffer size.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Ben Hutchings 2014-08-26 00:34:44 -07:00 committed by Greg Kroah-Hartman
parent 833c95456a
commit 655e5b7c03
1 changed files with 9 additions and 0 deletions
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9
drivers/base/core.c
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@ -2007,6 +2007,8 @@ create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
return 0;
pos += snprintf(hdr + pos, hdrlen - pos, "SUBSYSTEM=%s", subsys);
if (pos >= hdrlen)
goto overflow;
/*
* Add device identifier DEVICE=:
@ -2038,7 +2040,14 @@ create_syslog_header(const struct device *dev, char *hdr, size_t hdrlen)
"DEVICE=+%s:%s", subsys, dev_name(dev));
}
if (pos >= hdrlen)
goto overflow;
return pos;
overflow:
dev_WARN(dev, "device/subsystem name too long");
return 0;
}
int dev_vprintk_emit(int level, const struct device *dev,